Tibial trial prosthesis and bone preparation system

ABSTRACT

The method of implanting a femoral and a tibial knee prosthesis and instruments for surgically implanting the femoral and tibial prosthesis component as disclosed. The method includes the formation of a plurality of surgical cuts on the patient&#39;s distal femur. A trial tibial prosthesis is then fitted to the surgically prepared distal femur. The trial prosthesis has a femoral articulating surface and a non-articulating surface that fits the patient&#39;s distal femur at the surgical cuts. A surgeon then forms a transverse cut on the patient&#39;s proximal tibia. The surgeon places a tibial trial prosthesis on the patient&#39;s proximal tibia, the trial prosthesis including a tibial trial stem that fits the patient&#39;s intramedullary canal, a tibial trial metallic tray or plate, and a plastic trial insert that fits the tibial tray or plate. The plastic insert includes a tibial articulating surface that can articulate with the femoral articulating surface. The respective articulating surfaces are placed in contact and the surgeon then moves the patient&#39;s knee through a full range of motion. During this movement of patient&#39;s knee through a full range of motion, the surgeon uses a lever that is attached to the trial tibial prosthesis to rotate the trial tibial prosthesis about its stem. The surgeon can try different rotational positions of the tibial trial prosthesis each time moving the knee through a full range of motion to ensure proper orientation and an accurate fit.

This is a continuation of application Ser. No. 08/389,100, filed Feb.15, 1995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to orthopedic surgical instruments andsurgical methods and more particularly relates to an improved method andapparatus for installing a knee prosthesis with instrumentation thatallows a surgeon to rotate a tibial trial prothesis about the patient'sintramedullary canal axis with a lever while the patient's knee isflexed through a full range of motion and with a corresponding femoraltrial prosthesis in place.

2. General Background

In knee joint replacement surgery, a surgeon typically affixes twoprosthesis components to the patient's femur and tibia. Thesereplacement components are typically known as the femoral component andthe tibial component.

The femoral component is placed on a patient's distal femur after thesurgeon makes a plurality of surgical cuts. One common type of femoralprothesis has a J-shape. A femoral prosthesis is usually metallic,having a highly polished outer femoral articulating surface.

A common type of tibial prosthesis uses a laterally extending tray thatis shaped to conform to the patient's proximal tibia after the proximaltibia has been cut transversely by the surgeon. The tibia prosthesisalso includes a stem or plug that extends generally perpendicular to thetray and from the center of the tray. The stem is placed in a surgicallyformed opening that extends into the patient's intramedullary canal fromthe transverse cut formed on the proximal tibia.

A plastic, polymeric insert is attached to the tibial tray. This insertprovides a tibial articulating surface that articulates with the femoralarticulating surface as the patient's tibia moves through a full rangeof motion with respect to the patient's femur.

One of the problems with knee joint replacement surgery is that ofaccurately fitting the patient. Each patient has a different bonestructure and geometry. Even though the surgeon uses x-rays to study aparticular patient's anatomy at the knee, the surgeon does not have aperfect appreciation of the patient's anatomy until after the knee hasbeen surgically exposed and the surgeon begins to make cuts on the femurand the tibia.

Knee prosthetic components are not available in infinite sizes. Thesurgeon must examine the patient's anatomy, make the requisite surgicalcuts and install prosthesis components that fit.

A number of tibial components have been patented that relate to tibialcomponents having a tray, a plastic insert with articulating surface,and a stem portion that provides initial fixation when the prosthesis isimplanted. Other patents have issued that relate to cuttinginstrumentation for preparing the patient's proximal tibia to receive atibial prosthetic insert as part of knee joint replacement surgery.

The Murray Pat. No. 4,016,606 discloses a knee prosthesis that includesa tibial component with a tray and with a stem adapted to be received ina longitudinal bore in the patient's femur. The stem has one end that isintegral with a depending generally spheroidal surface having generallythe same radius as the radius of the spheroidal depression in theinsert.

In the Chiarizzio Pat. No. 4,601,289 there is disclosed a femoral trialprothesis/rasp assembly used in hip implant surgery. The assemblyincludes a handle that grips the combination trial prothesis/rasp in asecure manner by clamping over and locking on to a post on the trialprothesis/rasp which later serves as a mounting piece for a femoralprothesis head used in trial reductions.

A modular tibial prosthesis is disclosed in the Shaw Pat. No. 4,938,769.The Shaw patent discloses a tibial prosthesis for use during a totalknee arthroplasty procedure which includes a modular two part tibialcomponent comprising an in-bone anchorage assembly to which is removablyattached a tibial tray adapted to receive and retain a bearing insert.Removal of the tray permits access to the interface between the bone andanchorage assembly in the event removal or revision are necessary. Inpreferred embodiments, the invention affords hybrid fixation of thetibial prosthesis in that bone cement for immediate fixation andadaptation for longer term bone ingrowth are featured. Shaw alsodiscusses the use of porous coatings to enhance fixation.

U.S. Pat. No. 4,938,769 issued to James Shaw discloses an end boneanchorage assembly for a tibial prosthesis that includes an axiallyelongated central stem and a plurality of elongated fixation pegs spacedfrom the stem. The stem and the pegs have proximal and distal ends. Theproximal ends of the stem define an attachment table. A plurality ofstructural links interconnect the pegs and the stem. Means is providedfor removably attaching a tibial tray to the assembly wherein each ofthe pegs is connected to the stem by the structural link.

A tibial component for a replacement knee prosthesis is disclosed in theLawes et al. Pat. No. 5,080,675. Lawes discloses a tibial component fora replacement knee prosthesis comprising a tibial tray for connection toa suitably prepared tibia, the tray carrying fixed lateral and medialcondylar bearing components. Only the medial component has a shockabsorber located beneath it.

U.S. Pat. No. 5,137,536 issued to Tomihisa Koshino describes a tibialcomponent for an artificial knee joint. The tibial component includes aplate section having an upper surface and a pair of bearing surfacesparts that are adapted to be in sliding contact with a femoralcomponent. A stem portion extends downwardly from a lower surface of theplate section. A pair of blade like members extend obliquely andposteriorly from the stem. The plate section has a lower surface with aplurality of elongated grooves for improving affinity with respect tothe surrounding bone, the grooves including a first group of grooves anda second set of group of grooves extending perpendicularly to the firstgroup of grooves.

An example of a modular tibial support is seen in the Elias Pat. No.5,246,459 entitled "Modular Tibial Support Pegs for the Tibial Componentof a Prosthetic Knee Replacement System". The Elias Patent discloses amodular tibial support peg operable to secure a tibial component of aknee joint prothesis to a tibia having a groove. The modular tibialsupport peg includes a cylindrical body with a ridged outer surfaceoperable to engage the groove in the tibia. The modular tibial supportpeg further includes a plurality of spikes extending inferiorly from thecylindrical body. The spikes are operable to engage the tibia at theinferior end of the groove.

SUMMARY OF THE INVENTION

The present invention provides an improved method and apparatus forimplanting femoral and tibial prosthesis components. The surgeon firstforms a plurality of cuts on the patient's distal femur and fits afemoral trial prosthesis to the surgically prepared distal femur. Thefemoral trial prosthesis has an articulating surface for engaging acorresponding surface of a tibial prosthesis. The femoral trial also hasa non-articulating surface that fits the patient's distal femur at thesurgical cuts.

The surgeon forms a transverse cut on the patient's proximal tibia. Atibial trial prosthesis is then assembled from a plurality of componentsof different shapes and sizes. The tibial trial prosthesis is formed ofa trial tibial stem, a trial tibial tray or plate and a trial plasticinsert.

In the method of the present invention, a plurality of trays, aplurality of stems, and a plurality of plastic inserts are provided sothat the surgeon can custom construct a trial prosthesis with theseplurality of trial tibial prosthesis components.

Each of the plastic inserts has a tibial articulating surface thatarticulates with the femoral articulating surface of the trial femoralprosthesis.

During the surgery, the surgeon can place the femoral articulatingsurface against the selected tibial trial prosthesis articulatingsurface so that fit can be viewed before the actual prosthesiscomponents (i.e. tibial and femoral) are implanted. The surgeon can thenmove the patient's knee joint through a full range of motion duringwhich the femoral and tibial articulating surfaces of the correspondingtrial prosthesis components articulate with each other. With the presentinvention, the surgeon can adjust the relative rotational positions ofthese trial components before the final positions are fixed.

An instrument (preferably a lever with a handle) is provided forrotating the tibial trial prothesis about its trial stem so thatarticulation of the femoral trial prothesis and the tibial trialprosthesis can be observed. The surgeon can observe the fit between thetrial tibial and trial femoral prosthesis as the surgeon moves thepatient's knee through a full range of motion, and as the surgeonrotates the trial prosthesis into different rotational positions toobtain the best fit.

Using the method and apparatus of the present invention, the surgeon canbuild a custom "trial" tibial prosthesis to fit the patient's anatomyand then exactly position the tibial trial prosthesis in a desiredrotational position after repeatedly rotating the knee through a fullrange of motion. In using the method of the present invention, anoptimum fit is obtained. This method obtains correct orientation of theknee prosthesis through a full range of motion.

Once the surgeon determines that correct orientation of the components,the surgeon can pin both the femoral trial prothesis and the tibialtrial prosthesis to the underlying bone tissue.

The femoral trial prosthesis has openings that allow the surgeon todrill into the underlying tissue. Those openings receive pegs of thefinal actual femoral prosthesis component after the trial prosthesis isremoved. The surgeon rotates the tibial trial prosthesis until it is inan optimum position. The surgeon then pins the tibial trial prosthesisin position. The surgeon can remove the articular insert trial exposingthe tibial prep-plate. The surgeon the marks the tibia below thealignment marks on the tibial prep-plate. When using a non-porousimplant, the surgeon can remove the articular plastic insert trial andprepare for the distal fins on the implant using an appropriately sizedfin punch. If a long stem is desired, the surgeon can then ream up tothe stem diameter.

The surgeon places the tibial implant using marks that were made on thetibia when the trial prosthesis was in position, or using the cut madeby the fin punch. The fin punch is "stepped" to correspond to differentprosthesis sizes. The tibial prosthesis is installed using a tibialimpactor to seat the tibial implant on the proximal tibia. The surgeoncan use screws or cement to fasten the final selected tibial componentto the proximal tibia.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the presentinvention, reference should be had to the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich like parts are given like reference numerals, and wherein:

FIG. 1 is bottom view of the tibial prep-plate portion of the preferredembodiment of the apparatus of the present invention;

FIG. 2 is a top view of the tibial prep-plate portion of the preferredembodiment of the apparatus of the present invention;

FIG. 3 is a perspective view of the articular insert trial portion ofthe preferred embodiment of the apparatus of the present invention;

FIG. 4 is a bottom view of the articular insert trial portion of thepreferred embodiment of the apparatus of the present invention;

FIG. 5 is a perspective view of the articular insert trial rotationhandle portion of the preferred embodiment of the apparatus of thepresent invention;

FIG. 6 is a perspective view of the stem plug portion of the tibialtrial insert portion of the preferred embodiment of the apparatus of thepresent invention;

FIG. 6A is a top view of the plug of FIG. 6;

FIG. 6B is a bottom view of the plug of FIG. 6;

FIG. 7 is a schematic perspective view illustrating the trial tibialprosthesis and the trial rotation handle portions of the preferredembodiment of the apparatus of the present invention;

FIG. 8 is a schematic perspective view illustrating a resection of thepatella femoral groove, cutting along the medial and lateral sides ofthe femoral trial;

FIG. 9 illustrates the trial femoral prosthesis and the trial tibialprosthesis installed respectively on the patient's distal femur andproximal tibia and prior to rotation to the tibial trial prosthesis;

FIG. 10 is a schematic view illustrating rotation of the trial tibialprosthesis;

FIG. 11 is a schematic view illustrating a preparation of the proximaltibia to receive distal fins of a tibial implant using a fin punch;

FIG. 12 is a perspective view illustrating preparation for bone screwsfor the tibial tray;

FIG. 13 is a schematic perspective view illustrating attachment of theplastic insert of the tibia prosthesis to the tibial tray;

FIG. 14 is a partial sectional view of the tibial screw guide portion ofthe preferred embodiment of the apparatus of the present invention;

FIG. 15 is an elevational view of the tibial screw drill guide portionof the preferred embodiment of the apparatus of the present invention;

FIG. 16 is a partial bottom view of the tibial screw drill guide portionof the preferred embodiment of the apparatus of the present invention;

FIG. 17 is a partial top view of the tibial screw drill guide portion ofthe preferred embodiment of the apparatus of the present invention;

FIG. 18 is an elevational view of the preferred embodiment of the finpunch portion of the preferred embodiment of the apparatus of thepresent invention;

FIG. 19 is a perspective view illustrating the fin punch portion of thepreferred embodiment of the apparatus of the present invention;

FIG. 20 is a fragmentary sectional view illustrating the fin punch ofFIGS. 18-19;

FIG. 21 is another fragmentary sectional view illustrating the fin punchof FIGS. 18-19;

FIG. 22 is a perspective view of a second embodiment of a tibial trialprosthesis;

FIG. 23 is an elevational view of a second embodiment of the tibialtrial prosthesis;

FIG. 24 is an exploded perspective view of the trial taper portion ofthe second embodiment of the tibial trial prosthesis;

FIG. 25 is a fragmentary sectional view illustrating the trial stemcoupler of FIGS. 22-23;

FIG. 26 is a elevational view of the trial stem coupler of FIGS. 22-23;

FIG. 27 is a fragmentary sectional view illustrating the trial stemcoupler of FIGS. 22-23;

FIG. 28 is an end view illustrating the trial stem coupler of FIGS.22-23;

FIG. 29 is a fragmentary sectional view illustrating another trial stemcoupler;

FIG. 30 is an elevational view of another trial stem coupler;

FIG. 31 is an elevational view of the trial stem of FIGS. 22-23; and

FIG. 32 is fragmentary section view of the trial stem of FIGS. 22-23.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-4 and 7 show generally the preferred embodiment of the tibialtrial prosthesis of the present invention designated by the numeral 10in FIG. 7. Trial tibial prosthesis 10 is comprised of tray 11, stem orplug 12, and plastic insert 13. The entire trial prosthesis 10 can berotated after assembly and surgical placement on the patient's distaltibia 9 (see arrow 15 in FIG. 10.)

FIGS. 1-2 show trial tray or plate 11. Tray 11 includes an upper surface16 and a lower surface 17. A shoulder portion 19 extends partially aboutthe periphery 18 at the posterior of tray 11. A central V-shaped slot 20is provided for allowing a fin punch 43 to be used to make surgical cutsin the proximal tibia corresponding to fins that are a permanent part ofthe final tibial prosthesis to be implanted. In FIG. 11, the surgeonuses mallet 44 to drive fin punch 43.

The fin punch 43 is used after the tibial trial prosthesis 10 has beenfinally correctly oriented using the method of the present invention.Central opening 42 receives plug 12. Shoulders 37, 39 extend beyond theperiphery of opening 42. Plug 12 has proximal 36 and distal 35 ends. Aplurality of openings 21 can be provided in tray 11 for drilling holesthat will determine the position of bone screws that hold the finaltibial prosthesis to proximal tibia 9. A preferred embodiment of the finpunch will be described more full hereinafter.

A pair of spaced apart appendages 22, 23 extend away from the periphery18 of tray 11. The appendages 22, 23 (see FIGS. 1-2) have angledopenings 24, 25 for receiving bone spikes 26 (See FIG. 11). The openings24, 25 are circular in cross section to conform to the outer surface ofbone spikes 26. Each opening 24, 25 forms an acute angle with bottomsurface 17 of tray 11. This allows the surgeon to pin the trialprosthesis 10 to the patient's proximal tibia 9 after rotation has beenaccomplished using the lever 14 to determine the best fit of tray 11 onproximal tibia 9. Bone spikes 26 placed through the angled openings 22,23 fix the position of the tray 11 with respect to the patient'sproximal tibia 9 during punching of the V-shaped opening in thepatient's proximal tibia using a fin punch 43 (see FIG. 11).

In FIGS. 3-4, plastic trial insert 13 is shown. The insert 13 has a pairof concavities 28, 29 that define articulating surfaces that fit andarticulate with condylar portions of a femoral trial prosthesis 45mounted on the distal end 7 of the patient's femur 6 as shown FIG. 9.

A horizontal slot 30 extends from the periphery 18 of insert 13 towardthe center thereof. Slot 30 is generally parallel to the generally flatunderside 13A of insert 13, generally parallel thereto slot 13 ispositioned in between underside 13 and articulating surfaces 28, 29 asshown.

As shown in FIG. 4, the slot 30 terminates before reaching the anteriorside 31 of insert 13. A pair of annular shoulders 32, 33 retain thelever tab 34 at one end of line 14, and more particularly the tab end 34thereof so that rotation of the lever 14 also rotates the insert 13, thetray 11, and the plug or stem 12 to which tray 11 is affixed. In FIG.10, the entire assembly of tray 11, insert 13, and stem 12 are seenbeing rotated as illustrated by the curved arrow 15. Tab 34 can be usedto engage and manipulate insert 13. Thus, lever 14 and its tab 34 can beused to aid in removal of insert 13 from tray 11, or in attaching insert13 to tray 11.

In FIGS. 6, 6A and 6B, the trial stem 12 provides a distal end 35 thatis shaped to conform to the transverse cross section of opening 42 (seeFIG. 6B) and proximal end 36. The proximal end 36 has a pair of spacedapart shoulders 37, 39 that extend away from the central longitudinalaxis of the stem. Shoulders 37, 39 define a means of engaging the stem12 at top surface of the tray 11 upon assembly when the surgeon isbuilding a trial prosthesis.

The shoulders 37, 39 extend beyond the outer surface 41 of stem 12 andthus beyond the central opening 42 in tray 11. The slot 38 betweenshoulders 37, 39 allows the fin punch to fit between the shoulder 37,38. Slot 38 is positioned between the laterally extending shoulders 37,39, The slot 38 extends only about halfway along the length of the trialstem, terminating at surface 40.

In FIG. 8, the trial femoral prosthesis 45 is shown affixed to thepatient's distal femur 7. The distal femur is surgically prepared withanterior and posterior flat cuts that are parallel, a distal cut that isperpendicular to the anterior and posterior cuts, and chamfer cuts(anterior and posterior) that extend diagonally respectively between thedistal cut and the anterior and posterior cuts. Such a surgicalpreparation of the distal femur 7 to receive a femoral prosthesis, ortrial femoral prosthesis is known in the art.

The trial femoral prosthesis 45 of the present invention has a pair ofcurved articulating condylar surfaces 46, 47. The rear surface 48 oftrial femoral prosthesis 45 is sized and shaped to fit the surgicallyprepared distal femur 7. Trial femoral prosthesis 45 has a pair of flatcutting guide surfaces 49, 50 that allow the surgeon to form surgicalcuts 52, 53 forming a V-shaped recess in the patient's distal femur 7.Blade 54 in FIG. 8 is seen resecting the distal femur 7 with cuts 52, 53to form recess 51. The formed recess 51 allows placement of a finalfemoral prosthesis.

In FIGS. 9-10, trial tibial prosthesis 10 has been installed by thesurgeon on the patient's proximal tibial 9. The surgeon has alsoinstalled a trial femoral prosthesis 45 on the distal femur 7.

Using the method and apparatus of the present invention, the surgeon candetermine the best fit for the tibial trial prosthesis 10 in relation tothe trial femoral prosthesis 45. Trial femoral prosthesis 45 (FIG. 8)can be drilled at openings 55, 56 and affixed to the distal femur 7using bone screws or pegs. These openings 55, 56 can also define theposition of pegs that attach the final femoral prosthesis to the distalfemur 6.

In FIG. 10, the trial prosthesis 10 is shown mounted on the patient'sproximal tibia 9. Lever 14 fits slot 30 of the trial prosthesis insert13. Using the lever 14, the surgeon can now rotate the trial prosthesis10 about its stem portion 12, as shown by the curved arrows 15 in FIG.10. This can be done as the surgeon rotates the knee through its fullrange of motion to obtain the best fit.

The surgeon rotates the lever 14 to place the trial prosthesis 10 in adesired position (see FIG. 10). The surgeon can also rotate the tibiarelative to the femur (see arrow 27 in FIG. 9) through a full range ofmotion. If the surgeon is not satisfied with the fit, the lever 14 canbe used to reposition the trial prosthesis 10, and rotate the knee againthrough a full range of motion. The lever 14 and its tab 34 can also beused to change inserts 11, such as a different size or differentthickness insert 11. The procedure can be repeated until the surgeon iscompletely satisfied with the orientation of trial prosthesis 10 inrelation to trial femoral prosthesis 45.

In FIGS. 12 and 14-17, there can be seen screw drill guide 57. The drillguide 57 can be used to install a final tibial prosthesis 64 on thepatient's proximal tibia 9 once the surgeon has decided upon aparticular size and shape of tibial implant 64 based upon the use asaforedescribed of the tibial trial prosthesis 10. Drill guide 57includes a handle 58 for holding and manipulating the drill guide 57.

A guide sleeve 59 is generally cylindrically shaped, and provides aplurality of bores through bone screws can be placed for attaching thefinal tibial prosthesis 64 to the patient's proximal tibia 9. Guidesleeve 59 preferably includes four (4) screw guide bores. A straightbore 60 tracks the central longitudinal axis of guide sleeve 59. Aplurality of angles bores 61-63 extend from the upper surface to thelower surface of the guide sleeve 59, all of the bores 61-63 exiting atcommon opening 65.

In FIG. 12, there can be seen a drill 66 being guided by the surgeonthrough one of the bores 60-63 of the guide sleeve 59. The drill 66 issimply placed in the desired bore 60-63 and driven into one of theopenings 68 of the tibial prosthesis 64 using drill driver 67. Thesurgeon inserts a bone screw through the prepared hole then places thefinal plastic insert 69 on the prosthesis 64 and hammers it into placeusing mallet 44, hammering in the direction of arrow 70.

FIGS. 18-21 illustrate the all poly plastic fin punch of the presentinvention designated generally by the numeral 71, In FIGS. 1-2, finpunch 71 has a cylindrical section 72 with a pair of blades 73, 74joined at vertical plate 93 and extending downwardly with respect to thecentral axis of the cylindrical section 72. A horizonal frame section 76forms a connection between the cylindrical sections 72 and the pair ofblades 73, 74. A generally U-shaped slot 75 is positioned between theblade member 73, 74.

The horizontal section 76 has a generally flat upper surface 77. Each ofthe blades 73, 74 provides a respective inclined cutting edge 78, 79.The cutting edge 78 begins at pointed distal end 80 and extends tohorizontal surface 84 of section 76. The inclined cutting edge 79 beginsat pointed distal end 81 of blade 74 and extend to horizontal surface 84of section 76. A plurality of notches or stepped portions 85-90 can beseen along each of the inclined cutting surfaces 78, 79 of the blades73, 74.

Each of the stepped portions 85, 90 includes a vertical surface 91 and ahorizonal surface 92. The step portions combined with the size of slot20 of trial tray 11 to limit the depth of cut that is made by the finpunch 71. The punch 71 only goes down to that particular stepped portionor notch 85-90 that can be fitted through the slot 20 depending upon thewidth of the slot 20. For example, the punch 71 only goes down to thefourth notch for a size "4" tibial prep-plate 11 because the slots 20 inthe trial plate 11 for a size "4" or a given distance wide, They wouldbe provided as wider slots 20 for example on sizes "5" and "6". The slot20 would be smaller for an over all width for a size "3" or smaller,This sizing concept also corresponds to the implant design since thefins or blades 73, 74 get larger in width the larger the size.

FIGS. 22-32 illustrate tibial trial prosthesis 94 that can be used witha tibial prep plate tray 95. For purposes of the embodiment of FIGS.22-32, prep plate tray 95 can be assumed to have the same configurationand structure as tray 11 described in FIGS. 1 and 2.

FIGS. 22-23 show generally the second embodiment of the tibial trialprosthesis designated generally by the numeral 94. Tibial trialprosthesis 94 includes a prep plate or tray 95 that is attached to trialtaper 96, trial stem coupler 97 or 97A, and trial stem 98.

The trial taper 96 is shown generally in FIG. 24. Trial taper 96includes a generally cylindrical bushing 99 having an enlarged integralhead portion 100. An assembly bolt 101 can be placed through counterbore104 of bushing 99. The counterbore 104 is shaped to retain the head 103of bolt 101, allowing only the threaded section 102 to pass therethroughas shown in FIG. 24. Bushing 99 and its enlarged head 100 are coupled tostem 113 that has a frustoconical surface 113A thereon at the lowerdistal 105 end portion.

The coupler 97 has a frustoconically-shaped socket or bore 118. Trialstem taper 96 has a corresponding frustoconically-shaped projectingportion with surface 113A that forms a taper-lock fit with the socket118 of coupler 97.

The proximal 106 end of stem 113 provides a counterbore 107 that issized and shaped to receive bushing 99 and the threaded portion 102 ofbolt 101. Further, the counterbore 107 includes an internally threadedsection for engaging the threads 102 of bolt 101 upon assembly. The bolthead 103 can have a hexagonal recess, for example, for accepting anallen wrench that impart torque to the bolt 101 during assembly to stem113.

As with the trial tray 11 of FIGS. 1-2, a central opening 42 can beprovided into plate 95. The opening 92 is sized and shaped to receive areduced section 110 of stem 113 at proximal end 106 thereof. A thickened108 section of stem 113 extends between annular shoulder 109 andfrustoconical surface 113A, The thickened section 108 can carry a pairof longitudinally extending slots 111, 112 that receive the blades offin punch 71. Thus, the trial plate can have a V-shaped slot as with theslot 20 on plate ll of FIGS. 1-2. After the bushing 99, bolt 101 andstem 113 have been assembled, the slot 20 extends away from stem 113 andthe blades of fin punch 71 can pass on opposites sides of the trialtaper 96.

A flat surface 114 on stem 113 cooperates with a similar flat surface oftrial stem coupler 97, 98. In FIGS. 25, 28, a first trial stem coupler97 is shown. In FIGS. 29-32, a second trial stem coupler 97A is shownthat includes angled bore.

In FIGS. 25-28, trial stem coupler 99 includes an externally threadedsmaller diameter section 115 and a larger diameter cylindrical section116 that is unthreaded. The section 116 provides a frustoconical bore118 surrounded by a thick annular side wall 117 and a thin annular sidewall 122. An annular shoulder 120 extends between the thick annular sidewall 117 and the thin annular side wall 122. A transverse bore 119extends at generally right angles to the frustroconical bore 118 asshown in FIG. 25. Flat surface 121 is positioned at thin annular sidewall 122. The flat surface 121 mates with the flat surface 114 on stem113 upon assembly of trial taper 96 and coupler 97.

In FIGS. 29-32, coupler 97A is shown having an internal inclinedfrustoconical bore 126. The coupler 97A includes an externally threadedsmaller diameter section 123, a larger diameter unthreaded cylindricalsection 124 surrounded by a thick annular wall 125 and a thin annularwall 130. As with the coupler 97, the coupler 97A includes a transversebore 127. An annular shoulder 128 extends between the thick annular wall125 and the thin annular wall 130. A flat surface 129 at thin annularsurface 130 cooperates with a corresponding flat surface 114 on stem 113upon assembly of trial taper 96 and the trial stem coupler 97A.

In FIG. 29, axis 131 represents a normal axis that is the centrallongitudinal axis of threaded cylindrical section 123. The axis 132 isan offset axis that is the central longitudinal axis of inclinedfrustoconical bore 126. The angle between the normal axis 131 and theinclined axis 132 can be, for example, between about 3 and 8 degrees.

In FIGS. 31-32, the trial stem 98. Trial stem 98 includes a lowerfrustoconically-shaped distal end 133 a generally cylindrically-shapedelongated section 134, and a thickened proximal end portion 135. TheproxImal end portion provides an internally thread bore 136 that canform a connection with either the externally threaded section 115 oftrial stem coupler 97 or the externally threaded section 123 of trialcoupler 97A. Upon assembly, the flat annular surface 137 of proximal endportion 135 mates with the flat annular surface 138 of trial coupler 97or the flat annular surface 139 of trial coupler 97A.

The following table lists the parts numbers and parts descriptions asused herein and in the drawings attached hereto.

PARTS LIST

    ______________________________________                                        Part Number  Description                                                      ______________________________________                                        6            femur                                                            7            distal femur                                                     8            tibia                                                            9            distal tibia                                                     10           trial prosthesis                                                 11           tray                                                             12           stem                                                             13           insert                                                           13A          underside                                                        14           handle                                                           15           arrow                                                            16           upper surface                                                    17           lower surface                                                    18           periphery                                                        19           raised shoulder portion                                          20           V-shaped slot                                                    21           opening                                                          22           appendage                                                        23           appendage                                                        24           angled opening                                                   25           angled opening                                                   26           bone spike                                                       27           arrow                                                            28           concavity                                                        29           concavity                                                        30           slot                                                             31           anterior side                                                    32           shoulder                                                         33           shoulder                                                         34           tab                                                              35           distal end                                                       36           proximal end                                                     37           shoulder                                                         38           slot                                                             39           shoulder                                                         40           surface                                                          41           surface                                                          42           opening                                                          43           fin punch                                                        44           mallet                                                           45           trial femoral prosthesis                                         46           condylar articulating surface                                    47           condylar articulating surface                                    48           rear surface                                                     49           cutting guide surface                                            50           cutting guide surface                                            51           V-shaped recess                                                  52           surgical cut                                                     53           surgical cut                                                     54           blade                                                            55           opening                                                          56           opening                                                          57           screw drill guide                                                58           handle                                                           59           guide sleeve                                                     60           straight bore                                                    61           angled bore                                                      62           angled bore                                                      63           angled bore                                                      64           tibial prosthesis                                                65           common opening                                                   66           drill                                                            67           driver                                                           68           opening                                                          69           plastic insert                                                   70           arrow                                                            71           fin punch                                                        72           cylindrical section                                              73           blade                                                            74           blade                                                            75           slot                                                             76           horizontal section                                               77           flat surface                                                     78           inclined cutting edge                                            79           inclined cutting edge                                            80           pointed distal end                                               81           pointed distal end                                               82           proximal end                                                     83           internally threaded bore                                         84           horizontal surface                                               85           stepped portions                                                 86           stepped portions                                                 87           stepped portions                                                 88           stepped portions                                                 89           stepped portions                                                 90           stepped portions                                                 91           vertical surface                                                 92           horizontal surface                                               93           vertical plate                                                   94           tibial trial prosthesis                                          95           prep plate tray                                                  96           trial taper                                                      97           trial stem coupler                                               97A          trial stem coupler                                               98           trial stem                                                       99           bushing                                                          100          head                                                             101          bolt                                                             102          threads                                                          103          head                                                             104          counterbore                                                      105          distal end                                                       106          proximal end                                                     107          counterbore                                                      108          thickened section                                                109          annular shoulder                                                 110          reduced section                                                  111          longitudinal slot                                                112          longitudinal slot                                                113          stem                                                             113A         frustoconical surface                                            114          flat surface                                                     115          externally threaded section                                      116          cylindrical section                                              117          thick annulay side wall                                          118          frustoconical bore                                               119          transverse bore                                                  120          annular shoulder                                                 121          flat surface                                                     122          thin annular side wall                                           123          externally threaded section                                      124          cylindrical section                                              125          thick annular wall                                               126          inclined frustoconical bore                                      127          transverse bore                                                  128          annular shoulder                                                 129          flat surface                                                     130          thin annular wall                                                131          normal axis                                                      132          inclined axis                                                    133          distal end                                                       134          cylindrically-shaped section                                     135          proximal end                                                     136          internally threaded bore                                         137          flat annular surface                                             138          flat annular surface                                             139          flat annular surface                                             ______________________________________                                    

Because many varying and different embodiments may be made within thescope of the inventive concept herein taught, and because manymodifications may be made in the embodiments herein detailed inaccordance with the descriptive requirement of the law, it is to beunderstood that the details herein are to be interpreted as illustrativeand not in a limiting sense.

What is claimed as invention is:
 1. A trial prosthesis kit for trialattachment to a patient's long bone during knee joint replacementsurgery comprising:a) a trial prep tray member, the prep tray memberproviding a trial articulating surface and a connecting taper portion;b) a plurality of elongated trial stems, each having a generally uniformdiameter enabling the stem to fit within the patient's long boneintramedullary canal; and c) a pair of trial stem couplers that can eachform a connection between the taper portion and a selected trial stem,each of said couplers providing a shaped connecting surface that forms aconnection with a correspondingly-shaped connecting surface of the trialstem taper, the couplers defining different respective angularorientations between a selected trial prep tray member and a selectedtrial stem.
 2. The trial prosthesis kit of claim 1 wherein the couplercomprises a generally cylindrically-shaped body having a firstcylindrical section and a second cylindrical section, the second sectionhaving a larger diameter than the first section.
 3. The trial prosthesiskit of claim 1 wherein the coupler comprises an externally threadedsection and a non-threaded section having a socket, said socket beingsized and shaped to form a connection with the trial stem taper, thenon-threaded section having a larger diameter than the threaded section.4. The trial prosthesis kit of claim 1 wherein the prep plate trayprovides a central opening, and the trial stem taper forms a connectionto the prep plate tray at the opening.
 5. The trial prosthesis kit ofclaim 1 wherein the prep plate tray has a central opening and a V-shapednotch that communicates with the central opening.
 6. The trialprosthesis kit of claim 1 wherein there are at least a pair of saidcouplers that can be fitted one at a time to the trial stem and trialstem coupler, one of said couplers having a central longitudinal axisand a socket uniformly disposed about said axis.
 7. The trial prosthesiskit of claim 1 wherein the coupler has a frustoconically-shaped socketand the trial stem taper has a corresponding frustoconically-shapedprojecting portion that forms a connection with the socket of thecoupler.
 8. The trial prosthesis kit of claim 1 wherein the assembly ofthe trial taper, coupler, and trial stem has a generally uniformexternal diameter.
 9. The trial prosthesis kit of claim 1 wherein theassembly of the trial stem, coupler, and trial taper is generallycylindrically shaped.
 10. The trial prosthesis kit of claim 1 whereinthe stem has a connecting end portion that forms a connection with thecoupler, said end portion having a socket for receiving a projectingportion of the coupler.
 11. The trial prosthesis kit of claim 1 whereinsaid socket is internally threaded and wherein said coupler provides anexternally threaded section that forms a connection with the internallythreaded socket.
 12. A tibial trial prosthesis kit comprising:a) a prepplate tray having an opening therethrough; b) an elongated trial stemthat is capable of fitting inside the patient's intramedullary canal; c)a trial stem taper that is removably attachable to the prep plate trayat the opening; and d) a trial stem coupler that forms a connectionbetween the trial stem taper and the trial stem, said coupler comprisingfirst and second sections, the first section being smaller in diameterthan the second section, the first section adapted to form a connectionwith the top of the trial stem and the second section adapted to form aconnection with the bottom of the trial stem taper, said second sectionproviding a shaped connecting surface that forms a connection with acorrespondingly-shaped surface of the trial stem taper; e) wherein thereare at least a pair of said couplers that can be fitted one at a time tothe trial stem and trial stem taper, one of said couplers having acentral longitudinal axis and a socket uniformly disposed about saidaxis; and f) wherein at least one of said couplers has a centrallongitudinal axis and includes a socket having a socket axis that isangled with reference to the coupler axis.
 13. A trial prosthesis kitfor trial attachment to a patient's long bone during knee jointreplacement surgery comprising:a) a trial prep tray member, the preptray member providing a trial articulating surface; b) a plurality ofelongated trial stems, each having a generally uniform diameter enablingthe stem to fit within the patient's long bone intramedullary canal; c)a trial stem taper that is removably attachable to the prep tray member;and d) a pair of trial stem couplers that can each form a connectionbetween the trial stem taper and the trial stem, said couplerscomprising a first and a second section, the first section having asmaller diameter than the second section, wherein the first sectionforms a connection with the trial stem and the second section forms aconnection with the trial stem taper, said second section providing ashaped connecting surface that forms a connection with acorrespondingly-shaped connecting surface of the trial stem taper, thecouplers defining different angular orientations between a selectedtrial stem coupler and a selected trial stem; e) wherein there are atleast a pair of said couplers that can be fitted one at a time to thetrial stem and trial stem coupler, one of said couplers having a centrallongitudinal axis and a longitudinally extending socket uniformlydisposed about said axis; and f) wherein at least one of said couplershas a central longitudinal axis and includes a socket having a socketaxis that is angled with reference to the coupler axis.
 14. The trialprosthesis kit of claim 13 wherein the coupler comprises a generallycylindrically-shaped body having first and second cylindrical sections,the first section being of a smaller diameter than the secondcylindrical section.
 15. The trial prosthesis kit of claim 13 whereinthe coupler comprises an externally threaded section and a non-threadedsection having a socket, the non-threaded section having a largerdiameter than the threaded section said socket being sized and shaped toform a connection with the trial stem taper, said stem forming anattachment with said coupler at the threaded section of the coupler. 16.The trial prosthesis kit of claim 13 wherein the prep plate trayprovides a central opening, and the trial stem taper forms connection tothe prep plate tray at the central opening.
 17. The trial prosthesis kitof claim 13 wherein the prep plate member has a central opening and aV-shaped notch that communicates with the central opening.
 18. The trialprosthesis kit of claim 13 wherein the coupler has afrustoconically-shaped socket and the trial stem taper has acorresponding frustoconically-shaped projecting portion that forms ataper-lock fit with the socket of the coupler.
 19. The trial prosthesiskit of claim 13 wherein the assembly of the trial taper, coupler, andtrial stem has a generally uniform external diameter.
 20. The trialprosthesis kit of claim 13 wherein the assembly of the trial stem,coupler, and trial taper is generally cylindrically shaped.
 21. Thetrial prosthesis kit of claim 13 wherein the stem has a connecting endportion that forms a connection with the coupler, said end portionhaving a socket for receiving a projecting portion of the coupler. 22.The trial prosthesis kit of claim 21 wherein said socket is internallythreaded and wherein said coupler provides an externally threadedsection that forms a connection with the internally threaded socket.